F I S H and F I S H E R I E S , 2009, 10, 252–282 Voracious invader or benign feline? A review of the environmental biology of European catfish Silurus glanis in its native and introduced ranges* Gordon H Copp1,2, J Robert Britton2, Julien Cucherousset2,3, Emili Garcı´a-Berthou4, Ruth Kirk5, Edmund Peeler6 & Saulius Stakenas_ 7 1Salmon & Freshwater Fisheries Team, Centre for Environment, Fisheries & Aquaculture Science, Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK; 2Centre for Conservation Ecology, School of Conservation Sciences, Bournemouth University, Fern Barrow, Poole, Dorset, BH12 5BB, UK; 3EcoLab Laboratoire d’E´cologie Fonctionnelle, UMR 5245 (CNRS- UPS-INPT), Universite´ Paul Sabatier, Baˆt. 4R3, 118, route de Narbonne, F-31062 Toulouse, Cedex 9, France; 4Institute of Aquatic Ecology, University of Girona, E-17071 Girona, Spain; 5School of Life Sciences, Kingston University, Penrhyn Road, Kingston upon Thames, Surrey KT1 2EE, UK; 6Centre for Environment, Fisheries and Aquaculture Science, Weymouth, Dorset DT4 8UB, UK; 7Department of Freshwater Ecology, Institute of Ecology of Vilnius University, Akademijos 2, LT-08412, Vilnius, Lithuania Abstract Correspondence: A popular species for food and sport, the European catfish (Silurus glanis) is well-studied Gordon H Copp, Salmon & Freshwater in its native range, but little studied in its introduced range. Silurus glanis is the largest- Fisheries Team, Cen- bodied freshwater fish of Europe and is historically known to take a wide range of food tre for Environment, items including human remains. As a result of its piscivorous diet, S. glanis is assumed Fisheries & Aquacul- to be an invasive fish species presenting a risk to native species and ecosystems. To ture Science, Pakefield assess the potential risks of S. glanis introductions, published and ‘grey’ literature on Road, Lowestoft, Suf- folk NR33 0HT, UK the species’ environmental biology (but not aquaculture) was extensively reviewed. Tel.: +44 01502 Silurus glanis appears well adapted to, and sufficiently robust for, translocation and 527751 introduction outside its native range. A nest-guarding species, S. glanis is long-lived, Fax: +44 01502 rather sedentary and produces relatively fewer eggs per body mass than many fish 513865 species. It appears to establish relatively easily, although more so in warmer (i.e. E-mail: gordon.copp@ cefas.co.uk Mediterranean) than in northern countries (e.g. Belgium, UK). Telemetry data suggest that dispersal is linked to flooding/spates and human translation of the species. Received 9 May 2008 Potential impacts in its introduced European range include disease transmission, Accepted 12 November 2008 hybridization (in Greece with native endemic Aristotle’s catfish [Silurus aristotelis]), predation on native species and possibly the modification of food web structure in some regions. However, S. glanis has also been reported (France, Spain, Turkmenistan) to prey intensively on other non-native species and in its native Germany to be a poor biomanipulation tool for top-down predation of zooplanktivorous fishes. As such, S. glanis is unlikely to exert trophic pressure on native fishes except in circumstances where other human impacts are already in force. In summary, virtually all aspects of the environmental biology of introduced S. glanis require further study to determine the potential risks of its introduction to novel environments. Keywords Diet,distribution,environmentalimpact,growth,habitatuse,reproduction *This article ‘‘Voracious invader or benign feline? A review of the environment biology of European catfish Silurus glanis in its native and introduced ranges’’ was written by Gordon H Copp of Cefas-Lowestoft, J Robert Britton and Julien Cucherousset of Bournemouth University, Emili Garcı´a- Berthou of University of Girona, Ruth Kirk of Kingston University, Edmund Peeler of Cefas-Weymouth and Saulius Stakenas_ of Institute of Ecology of Vilnius University. It is published with the permission of the Controller of HMSO and the Queen’s Printer for Scotland. 252 DOI: 10.1111/j.1467-2979.2008.00321.x Ó 2009 Crown copyright Environmental and invasion biology of Silurus glanis G H Copp et al. Introduction 253 Description and morphology 254 General description 254 Morphology (relative growth) 255 Distribution and habitat 255 Native distribution 255 Non-native distribution 256 Habitat use 257 Natural diet 257 Senses and detection of prey 257 Prey selectivity or preference 258 Ontogenetic changes in diet 260 Seasonal changes in diet 262 Age and growth 263 Age and ageing 263 Ontogeny and growth 263 Sexual growth dimorphism 264 Geographical variation in growth rates 264 Reproduction 265 Sexual maturation and gonad development cycle 268 Reproductive behaviour 269 Absolute and relative fecundity 269 Parasites and pathogens 270 Viruses and bacteria 270 Eukaryotic parasites 270 Reflections on the species’ potential 272 invasiveness and ecological impacts Acknowledgements 275 References 275 been published on the environmental biology of Introduction introduced S. glanis populations and even less Non-native fish introductions have a long history in information is available on the species’ impact on Europe (Copp et al. 2005a) and one of the most native biota and ecosystems in its introduced popular of the successful introductions has been European range. This is perhaps not surprising for that of the European catfish (Silurus glanis, Siluri- countries where S. glanis has been introduced dae). The largest freshwater fish species indigenous in recent decades (e.g. Spain), but it is remarkable to the European continent, S. glanis is native to for other European locations such as the United Eastern Europe and western Asia (Kinzelbach Kingdom, where there is only limited data in 1992), but is now established in at least seven scientific publications in reference to its general countries to the west and south of its native range distribution (Hickley and Chare 2004), growth and (Elvira 2001). S. glanis, which is among the 20 angler recapture rates (Britton et al. 2007) and low largest freshwater fish species worldwide (Stone abundance in the River Thames (Kirk et al. 2002; 2007), is particularly popular amongst European Copp et al. 2007). In light of this paucity of anglers and the species has been the subject of information, the aim of the present paper was to numerous studies related to its increasing use in review the published (peer and grey) literature on aquaculture. However, relatively few studies have the environmental biology of S. glanis in its native Ó 2009 Crown copyright, F I S H and F I S H E R I E S , 10, 252–282 253 Environmental and invasion biology of Silurus glanis G H Copp et al. and introduced European range as a surrogate recreational fisheries as well as in aquaculture (Berg means of assessing the species potential risk to 1949; Ada´mek et al. 1999). The species is a sport native species and ecosystems in those parts of fish in some countries (e.g. France, Italy, Spain, UK) Europe where the species is not native (i.e. absent and considered a delicacy in others (e.g. Hungary, since the last glaciation). This review encompasses Poland, Slovakia, Lithuania), where it is exploited all aspects of the species’ morphology, distribution, for its flesh (tender white meat), skin (for leather habitat use, migratory behaviour, diet, growth, and glue production) and eggs (for caviar). The diseases, and reproduction under natural conditions economic importance of S. glanis in many central and, as such, excludes all papers dealing with the and eastern European countries has increased aquaculture of S. glanis unless they have a direct because the species possesses many characteristics bearing on the species’ environmental biology. The desirable for profitable aquaculture (Proteau et al. review is concluded with a general discussion on the 1993; Paschos et al. 2004) leading to a proliferation species’ potential invasiveness and consequential of scientific articles on its reproduction, genome threat to native species and ecosystems. manipulation and management (Schlumberger et al. 1995; Ada´mek et al. 1999; Triantafyllidis et al. 2002; Alp et al. 2004). In 1993, estimates of Description and morphology aquaculture production of S. glanis in Europe (excluding the former USSR) range from 358 tonnes General description (Haffray et al. 1998) to 602 tonnes (for 10 Euro- Silurus is the only existing genus in Europe of the pean countries; Linhart et al. 2002) in 1993, rising Siluridae family (Ferraris 2007), with the other in 2002 to about 2000 tonnes (Linhart et al. 2002) genera confined to Central and South-East Asia and research on husbandry of the species continues (Berg 1949; Maitland and Campbell 1992; Teugels (Paschos et al. 2004; David 2006). 1996). There are 18 Silurus species of which two S. glanis has an elongated body that is laterally are native to Europe: Aristotle’s catfish (Silurus decompressed behind its broad head, which aristotelis, Siluridae) is endemic to Greece (Phillips accounts for about 20% of the entire body length and Rix 1988) and S. glanis is native to mainland and has a rounded, flattened snout and widely- Europe, east of the River Rhine (Fig. 1). However, spaced nostrils anterior to the olfactory cavities S. glanis has been introduced into a number of (Miha´lik 1995). S. glanis has a triangular-shaped countries in Western Europe, such as the UK head (Cˇerny´ 1988) with small eyes and a large in the 19th century (Lever 1977) and Spain in mouth, with two very long, slender, flexible carti- the 20th century (Elvira and Almodo´var 2001; laginous barbs on the upper jaw (up to 41.2% of TL; Schlumberger et al. 2001), and re-introduced after a Mukhamediyeva and Sal’nikov 1980) and four long absence to previously native distributions in short, flexible barbs, which protrude below the parts of Belgium, the Netherlands and France (Van lower jaw (Davies et al. 2004). These reach as far as Neer and Ervynck 1993; Volz 1994). S. glanis is an the base of the pectoral fins and are, on average, economically important species in commercial and 11.4% of the fish’s TL (Miha´lik 1995), although in Figure 1 Native (n) and introduced (n) distributional ranges of S.